1. Field of the Invention
The present invention relates to a patch for tooth whitening. More particularly, the present invention relates to a patch for tooth whitening, comprising a tooth-adhering layer (1) containing erodible polymer complexes formed by hydrogen bonding of a polymer with a carboxyl group (—COOH) and a polymer with a carbonyl group (—C═O) or ether group (—O—) and a tooth whitening agent; and an erosion rate-controlling layer (2) containing a mixture of a hydrophilic polymer and a film-forming polymer, wherein the patch is in a film form and is characterized by being eroded until extinguished after releasing the tooth whitening agent.
2. Description of the Prior Art
A tooth is composed of an inner dentine layer and an outer hard enamel layer functioning to protect the inner parts of the teeth from infection and decay. The enamel layer is composed of about 96% inorganic matter and about 4% organic matter and water. The inorganic crystals themselves are colorless and transparent. However, spaces exist between the inorganic mineral crystals, which contain organic materials including proteins. Staining substances often penetrate the spaces, thus leading to a yellow staining of the teeth. For this reason, a lot of efforts have been made to make transparent or white teeth.
Among the tooth whitening products currently available, fluoride-containing toothpaste is effective in chemically removing stains on the teeth, which are generated by absorbance of food debris, nicotine, coffee or black tea and the like to the teeth surfaces, or by staining of the tartar or soft precipitates on the teeth surfaces with staining substances. Toothpaste is typically used to obtain a clean feeling in the mouth or to freshen the breath. However, tooth whitening is difficult to be achieved just by brushing the teeth with the toothpaste.
In the 1960's, an American dentist stumbled upon during treating patients with gum disease the fact that hydrogen peroxide used in gum disease treatment bleach the teeth, and developed a tooth-whitening agent that is both effective and safe.
In addition, a first home-usable tooth-whitening apparatus was developed in the end of the 1980's, which uses a night guard generally containing a hydrogen peroxide or carbamide peroxide gel. Currently, such a method is the most popular in tooth whitening. However, since the peroxide gel is used in a high concentration, such a method is problematic with respect to convenience in use and safety, such as the case that gum is irritated by the excessive peroxide gel and a tray.
To solve these problems, various tooth-whitening products have been developed by employing peroxides of low concentrations without use of the mouth tray.
U.S. Pat. Nos. 5,879,691, 5,891,453 and 5,989,569 and International Pat. Publication No. WO98/55044, which are owned or were applied by the Procter & Gamble Company, disclose delivery systems for a tooth-whitening substance, which are characterized by coating a polyethylene film instead of a mouth tray with a carbamide gel containing a peroxide as a tooth whitening agent and then contacting the gel onto a surface of the teeth. These systems have improved simplicity in use in terms of not using the mouth tray. However, such systems, which employed the whitening agent in a gel phase just applied onto the film, have drawbacks in that the peroxide gel is apt to stick to the hands or tongue, gum, etc. upon its application onto the teeth surfaces and the polyethylene film must be removed after a prescribed time.
Japanese Pat. Laid-open Publication No. Heisei. 10-17448, applied by the Lion Company, discloses a mouth-pasting agent of sheet form sheet, comprising kojic acid, kojic salts or kojic derivatives. The mouth-pasting agent comprises a tooth-adhering layer and a backing layer, wherein the tooth-adhering layer contains a water-soluble polymer such as polyvinylalcohol and the backing layer contains a water-insoluble polymer such as ethyl cellulose. However, polyvinylalcohol has a poor tooth-adhering property. Also, since all of the used whitening agents have strong acidity, they can cause irritation in accordance with pH in the mouth.
U.S. Pat. No. 5,425,953, filed by the Perio Company, discloses a sustained-release film-forming liquid polymer composition comprising a water-soluble cellulose polymer such as hydroxypropyl cellulose, a peroxy compound, a peroxy compound-stabilizing agent such as EDTA and a solvent such as water or ethanol. The liquid polymer composition, which is in a film-forming formulation at the tooth surface, can attribute stabilization of the peroxy compound, but can cause irritation in the other mucous membranes in the mouth before the liquid composition forms a film.
U.S. Pat. Nos. 6,419,906, 6,503,486 and 6,514,483, granted to the Colgate Company, disclose film formulations prepared by mixing polyethylene oxide with peroxides. However, use of only polyethylene oxide does not give sufficient adhering ability to the teeth surfaces to the film. In addition, the film is rapidly solubilized in the mouth and thus does not guarantee a sufficient time for release of the peroxide in a desired amount. Furthermore, since the film is composed of only a tooth-adhering layer, it often adheres to the mucous membranes as well as the teeth, and thus is very inconvenient.
Korean Pat. Laid-open Publication Nos. 10-2002-96264, 10-2002-97297, 10-2002-97298, 10-2003-299, 10-2003-1297 and 10-2003-3973, applied by the LG Household & Health Care Ltd., disclose dry-type patches for tooth whitening, which are prepared by mixing a hydrophilic polymer such as polyvinylpyrrolidone with peroxides, a peroxide-stabilizing agent and the like. In order to prepare such dry-type patches, a tooth-adhering layer and a backing layer are required. The tooth-adhering layer contains a hydrophilic polymer, which cannot adhere to the teeth surfaces or has a weak adhesive strength under a dry condition, and, when the whitening agent is applied to a desired area of the teeth and then hydrated by a small amount of water thereon, come to have an ability to adhere to the teeth surfaces or a strong adhesive strength. The backing layer is composed of essentially a water-insoluble polymer such as ethyl cellulose to protect the tooth-adhering layer. However, these kinds of patches are inconvenient in use since they must be removed after being applied to the teeth during a prescribed time. Also, the patches require caution in use due to the following reason. When hydration makes very rapid progress and thus, the patches loses adhesive strength, the whole or a portion of the backing layer may be detached from the patches and stick in one's throat, thereby causing safety risks.
As described above, because of comprising a backing layer, the conventional patches associated with tooth whitening have several disadvantages including inconvenience of being essentially removed from the teeth after use during a prescribed period, safety risks caused by its weakened adhesive strength capable of leading the water-insoluble backing layer detached from the applied teeth to be caught in the esophagus or airway, and obstruction sensation in the teeth or the mouth.
Thus, through a thorough and intensive research, the present inventors prepared a patch for tooth whitening by employing polymer complexes having an erosion property of various rates. Research resulted in the finding that the patch has a tooth-whitening effect identical to the conventional tooth whitening patches as well as being eroded and eventually completely distinguished on the teeth after use, thereby solving the inconvenient problem requiring separate removal of the patch from its applied teeth.